Coupling process of aromatic compounds

ABSTRACT

Oxydative coupling process of aromatic compounds having at least two hydrogen atoms in the aromatic nucleus, characterized by that the aromatic compounds are dehydrogenated in oxygen or oxygencontaining gas under pressure in the presence of an organic palladium compound as a catalyst.

ilnite States atom ltatani et a1.

[ COUPLING PROCESS OF AROMATIC COMPOUNDS [75} Inventors: Hiroshi Itatani; Hataaki Yoshimoto,

both of Chiba, Japan [731 Assignee: Ube Industries, Ltd., Yamaguchi,

Japan [22] Filed: Dec. 10, 1971 i211 .Appl. No.1 206,950

[30} Foreign Application Priority Data Dec. 22, 1970 Japan 115123/70 [52] US. Cl." 260/479 R; 260/488 CD; 260/613 R; 260/645; 260/649 DP; 260/670 [51] Int. Cl C07c 69/14; C070 15/14 [58] Field of'Search 260/479 R, 670

[56] References Cited UNITED STATES PATENTS 3.493 605 2/1970 Selwitz 260/488 July 15, 1975 3,644,486 2/1972 Boldt et a1. 260/479 3,651,127 3/1972 Hornig et a1 260/479 OTHER PUBLICATIONS Van Helden et al., Recueil, Vol. 84, (1965), p. 1268. Davidson et al., March, 1966, p. 457.

Davidson et al., August, 1967, p. 1361.

Davidson et al., J. Chem. Soc. (Sect. A), (1968), pp. 1331-1334.

Primary Examiner-James A. Patten Attorney, Agent, or Firm-Henderson, Farabow & Garrett Finnegan 5 7 ABSTRACT 7 Claims, N0 Drawings COUPLING PROCESS OF AROMATIC COMPOUNDS This invention relates to a process for obtaining oxydative coupling compounds with excellent efficiency by oxydative coupling of aromatic compounds.

This invention more particularly relates to an oxydative coupling process of aromatic compounds, wherein aromatic compounds having at least two hydrogen atoms in the aromatic nucleus are dehydrogenated in oxygen or oxygen-containing gas under pressure in the presence of an organic palladium compound as a catalyst.

Heretofore it has been known that aromatic compounds. for example, toluene, are oxydatively coupled in the presence of palladium salts such as palladium chloride, palladium acetate, mixed with acetic acid and sodium acetate to obtain bitolyls (refer to R. Van. Helden and G. Verberg: Rec. Trav. chim 84,1263 (1965) and .l. M. Davidson and C.- Triggs: J. Chem. Soc, (A), 1331 (1968) When employing these known processes, however, there are such disadvantages that the yield of bitolyl is very low and that palladium black is precipitated in the reaction system (metallic black).

Another process, for example, disclosed in the Japanese Official Gazette (Japanese Patent Publication No. 26717/1964), describes the process for producing 3, 3', 4, 4'-tetramethyl-biphenyl, biphenyl or diisopropylbiphenyl, wherein aromatic compounds, for example o-xylene, benzene or cumene, react with pa]- ladium or platinum salts in the presence of salts of alkali metals and organic acid.

The said process, however, depends on the reaction of aromatic compounds and platinum or palladium salts and therefore the yield of coupling compounds obtained is less than 100 mol per cent based on palladium or platinum salts. Further, there is such a disadvantage that a large portion of palladium salt or platinum metal precipitates in the reaction system. Therefore it is impossible to obtain a high yield of coupling compounds according to said process.

The present invention is an improvement in regard to the inventors previous study that the coupling reaction can be oxydatively attained leaving no Pd-black in the system by reacting aromatic hydrocarbons with olefines in an atmosphere where the partial pressure of oxygen is higher than 2 kg/cm in the presence of catalytically reacting Pd-salts. (Refer to Japanese Patent application No. 92041/68).

According to the present invention aromatic compounds are oxydatively coupled by the use of organic palladium compounds and the coupling compounds can be produced with excellent yields; furthermore, the precipitation of palladium black can be prevented and the oxydative coupled aromatic compounds can be produced with surprisingly high yields without any further additives such as sodium acetate to the reaction system.

Thus, this invention provides a process which comprises oxydatively coupling aromatic compounds having at least two hydrogen atoms in the aromatic nucleus, under elevated pressure of oxygen or oxygencontaining gas in the presence of an organic palladium compound as a catalyst.

According to the present invention, it is particularly important that the coupling reaction shall be carried out in oxygen gas or oxygen-containing gas under an elevated pressure. If the pressure conditions are not met an oxydative coupling reaction is hardly possible to take place.

For this invention, it is preferable to carry out the re- 5 action under the partial oxygen pressure of 5 300 kg/cm preferably 5 40 kg/cm Under a pressure below 5 kg/cm the reaction does not proceed and if the pressure exceeds 300 kg/cm there is no increase in yield.

Therefore, it is not practical to cause the reaction to take place under a partial oxygen pressure higher than the above mentioned pressure.

Oxygen gas used for the present invention may be elemental oxygen, but it is preferable, for the prevention of an explosion, to use it mixed with an inert gas such as nitrogen gas, carbon dioxide gas and/or rare gas, such as air.

In the presence of any compounds other than the organic palladium salt like sodium acetate, potassium acetate, lithium chloride, potassium nitrate, lithium nitrate, potassium sulfate, acetic acid, sulfuric acid, polar solvent such as dimethylformamide and acetonitrile and water, the amount of the coupled product obtained by oxydation is extremely small or can not be produced at all and in some cases an explosion occurs during the reaction. Likewise, even if aliphatic olefines like cyclooctadiene or cyclo-dodecatriene is used for the reaction system mentioned above, the reaction does not proceed at all.

Therefore, it is essential that the reaction be carried out without any of said compounds being present. Further, through the employment of some additives, for example, B-diketones such as acetylacetone, benzoylacetone, trifluoroacetone, hexafluoroacetylacetone and benzoyltrifluoroacetone in the reaction system, the yield of the coupling compounds can be greatly improved.

In case that the coupling reaction is carried out in an autoclave made of stainless steel or steel, some metal salts like iron, nickel or chromium salt will precipitate, thereby preventing the oxydative coupling reaction from taking place. The use of ethylenediaminetetraacetic acid as an additive can promote the reaction effectively.

The amount of the additive such as B-diketones, ethylenediaminetetraacetic acid is 0.5 4 moles based on the organic palladium compound, more preferably in equal molarity.

The catalyst used in this invention should be an organic palladium compound. In order to produce oxydative coupling compounds with excellent yield, it is desirable to use aliphatic monocarboxylic acid salts having 1 5 carbon atoms, like palladium formate, palladium acetate palladium propionate, palladium butyrate, palladium valerate, etc. It is also preferable to use palladium benzoate, palladium acetylacetonate, bis-dibenzylideneacetone palladium etc. Particularly palladium acetate is preferable.

According to this invention, it is not desirable .to use inorganic palladium salts such as palladium chloride, nor a mixture of palladium chloride and sodium acetate etc.

The amount of palladium salt catalyst used in this invention is 1/ l 10000 mol based on the aromatic compounds and more preferably 1/200 l/2000 mol.

Because palladium black does not precipitate in the reaction system during the coupling reaction of the aromatic compounds. the itl'} iii-lk ptilltidiiiiii compounds can be easily I'Ctltncrttl and iegeiieiatcd according; \(i the process of the present ltl'it'l'illtti For example. the atmosphere in the autocla e l\ suiisiituied with niiio gen gas after the reaction and then tilled up with li\dri gen gas. reducing thereby the ',iall.tdiuni salt contents in the reaction solution .ii.d precipitating palladium black. Then the palladium black is dissoh ed in nitric acid. the solution filtered and atetic acid. propionic acid etc. are added.

The aromatic compounds u ed in the pri cess of the invention should htiie at least two h drogen tlli l'iis in the aromatic nucleus lliese ni llitillc compounds tire represented by the tollowinu general formula (wherein R is selected tron. inc group consisting of hydrogen atom. tilliyl haung 5 carbon atoms. alkanoyloxy ha ing l 5 carbon atoms. cillult}. having 1 5 carbon atoms substituted tllliil the substituted group is selected from LiCCIyl ind halogen) nitroand halogen i1 is i) 4 but u hen n is Q 4. R tnti be the same or a different substitaent from a Aromatic cll'iiPUUl'lLlS represented by the general for mula are. for etanipld hen/cue. toluene. o mor p) cth I -cn/ene. ll. -tnmethylhenzene.

t'luorooenuiie.

nitrotoluene, o-

xylene. chlot'otnttii'vll tn/ene. chli I T'klt/L'Ilk anisole lllif't t'li/Lnc. o in chlorotoluenc. I -dinietliu.i' cii/ylacetate. \ylylened iacetate. triiluoiwitoluene. phenylaeetate. niethylacetyl salicylate and the like.

The aromatic compound used for the process of the present invention is an aromatic compound hi1\lng at least two hydrogen atoms in the aromatic nucleus A substituted group R ha ing actiic hydrogen in the form of OH. --NH (OOH is not preferred.

With respect to the TC'dctlUli temperature it is preferable that the reaction process is carried out at a tent perature ranging from room temperature to .ibU( es pecially from till to lon t. ioueh it zirie depending on the aromatic compound used and the partial pressure of oxygen in the reaction system.

The recovery from [he rcattion solution oi itilil pounds which have not been ci iipleil by U.v!.llill( ll effected easily in a conventional way. for example b the evaporation process of the reaction solution According to the present inwntion tor e\".tr ip.c a. ramethylbiphenyl can i, btained with :-ci ll\fi from owylcne and the): :h lill Lll}lisrll tlkufl kfl tic Lilillttl couplin 4 pound is oxydi/cd and iiiaiix acid can be obtained lhe rcsuiti itt carhomiic acnl l very useful as J raw mater: ii iii: tonipouiids such a linntcd ii W ml of toluene And 0.112 g (0.5 m mol) of palla' tliuni acetate were introduced into a stainless steel au toelme of lit) nil capacity ol" the electromagnetically agitating t pe and pure oxygen gas was introduced into the autocla e till the inner pressure thereof reached 50 ltg cm lhen the ox'ydative coupling reaction of toluene was it) carried out at l-l()( for 4 hours Alter the reaction the reaction solution in the auto claie was analyzed ny means of gas-chromatography. 1 Mg i bitoiyl yield of $060 mol 7( based on pallti' diuni acetate 2. i) (11g ot benzylacetate (yield of 30 m l l "I based on palladium acetate) and 004g of dihenzyl iyield of -15 mol based on palladium acetate) were obtained The reaction solution was concentrated in an oil bath at HUT lheii precipitates were separated from it. The filtered solution was concentrated on the oil bath at ltitVC under reduced pressure. Thus 5.65g of brown liquid was obtained. After distillation under reduced pressure 14b of hitolyl (yield of 2.640 mol '71 based on palladium acetate) was obtained 6 types of isomers were observed in the bitolyl obtained and the percentages thereof were as follows nth 1.)4. o rn'- 14.8%. o.p'- 10.5%. m,m'- 29.6 71. tii p'- no"; and pp 9.2% respectively Precipitation of palladium black was not observed after the reaction.

(fonttol 1 An oxydatii e coupling reaction oi" toluene was carried out tinder the same conditions as those of Example except that the pressure of oitygcn was atmospheric pressure No oxydati e coupling reaction did occur. Control I Ufiml of toluene. 021g of palladium acetate, 1.0g of sodium acetate and l ml of acetic acid were introduced into the same autoclzne as in Example 1, and pure oxygen gas was introduced into the autoclave till the inner pressure thereof reached lUU kg/cm Then oxydative coupling reaction was carried out at 100C for 4 hours.

titer the reaction. the reaction solution in the autoc ave was" reated in the same way as in Example 1 and 1-1; of hiiolyl iyield of 82 mol based on palladium tieetatei w as intaiiied Control 3 Wu ml of toluene. 022g of palladium acetate and ltllig of sulfuric acid were introduced into the same autoclave as in Example 1 and a gaseous mixture of nitrogen and oxygen i l 1 mol ratio) was introduced into the autocla e till the inner pressure thereof reached 50 t ni .c: the reactiix-n. the reaction solution in the auto claw t\ i\ treated the same way as in Example l but no more than ti trace ot bitolyi was obtained.

EXAMPLE 2 t;r- :ssel containing 50 ml of toluene and 0.] 12g i at :iailadiiiiii acetate was placed in a stain .ittciaa c oi" the shaking type (300 ml capac- Minn a gaseoa. znittuie of nitrogen and oxygen lzl [.illt .yiis inti'onuced into the autoclave till the: liilltl ressure tl'lkfici 1 reached 50 l\g/CIll and an ox- Sil tia iz )3 coupling reaction was carried out illtll ydative coupling reaction was carried out at 120C for 4 hours.

After the reaction, the reaction solution in the autoclave was treated in the same way as in Example 1 and 165g of bitolyl (yield of 1,812 mol based on palladium acetate) was obtained.

Control 4 An oxydative coupling reaction of toluene was carried out under the same conditions as those in Example 2 except that 0.112g (0.5m mol) of palladium nitrate instead of palladium acetate was used.

No bitolyl was obtained.

Control 5 An oxydative coupling reaction of toluene was carried out under the same conditions as those in Example 2 except that palladium chloride (0.5m mol) and potassium acetate (2.5m mol) were used instead of palladium acetate.

As a result, 185 mol of bitolyl based on palladium was formed.

EXAMPLES 36 An oxydative coupling reaction of toluene was carried out under the same conditions as those in Example 2 except that a gaseous mixture of nitrogen and oxygen (r, 1:1 mol ratio) was introduced till the inner pressures of the autoclave reached the various pressures shown in Table 1.

After the reaction, the reaction solution was treated in the same way as in Example 1, and the results shown in Table l were obtained.

An oxydative coupling reaction of o-nitrotoluene was carried out under the same conditions as those in Example 2 except that 50ml of o-nitrotoluene was used instead of toluene.

After the reaction, the reaction solution was treated in the same way as in Example 1 and 301g of dimethyldinitrobiphenyl (yield of 2,210 mol based on palladium acetate) was obtained.

EXAMPLE 8 An oxydative coupling reaction of anisole was carried out at 130C for 8 hours under the same conditions as in Example 2 except that 50ml of anisole instead of toluene was used.

As a result, the yield of dimethoxybiphenyl was 2,050 mol based on palladium acetate.

EXAMPLE 9 .An oxydative coupling reaction of p-xylene was carried out at 150C for 12 hours under the same conditions as in Example 2 except that 50ml of p-xylene instead of toluene was used.

As a result, the yield of tetramethylbiphenyl was 1.420 mol percent based on palladium acetate.

EXAMPLE 10 An oxydative coupling reaction of toluene was carried out at C for 5 hours under the same conditions as in Example 2 except that 0.5m mol of palladium benzoate instead of palladium acetate was used.

As a result, the yield of bitolyl was 3,400 mol based on palladium benzoate.

EXAMPLE 1 1 An oxydative coupling reaction of o-chlorotoluene was carried out at 150C for 5 hours under the same conditions as in Example 2 except that 50ml of ochlorotoluene instead of toluene was used.

As a result, the yield of dichlorobitolyl was 1,520 mol based on palladium acetate.

EXAMPLE 12 A 1,000m1 glass vessel containing 0.224g (1m mol) of palladium acetate, 300ml of toluene and 0. lg of acetylacetone was placed in an autoclave, a gaseous mixture of nitrogen and oxygen (1 1 mol ratio) was introduced into the vessel and an oxydative coupling reaction was carried out at 150C under the pressure of 65 kg/cm for 16 hours.

The reaction solution was treated in a similar way to Example 1 and 30.8g of bitolyl (yield of 16,900 mol based on palladium acetate) was obtained.

EXAMPLE 13 An oxydative coupling reaction of benzylacetate was carried out under the same conditions as in Example 1, except that 50ml of benzylacetate instead of toluene was used.

The reaction product was treated in the same way as in Example 1 and the yield of diacetoxymethylbiphenyl was 2,000 mol based on palladium acetate.

EXAMPLE 14 EXAMPLES 15-23 Oxydative coupling reactions were carried out in a similar way to Example 14, except that toluene, oxylene, m-xylene, p-xylene, trifluorobenzene, chlorobenzene, trifluoromethyl-benzene, nitrobenzene, phenylacetate, were used instead of benzene.

After the reactions, the reaction solutions were treated in the same way as in Example 1, and the results shown in Table 2 were obtained.

Table 2 yield of coupled compound based on No. palladium of aromatic coupled acetate Example compound compound (mol 71) 15 toluene bitolyl 7.410 16 o-xylene tetramethyl- 5.670

biphenyl l7 m-xylene tetramethyl- 4.130

biphenyl l8 p-xylene tetramethyl- 400 biphenyl l9 fluorobenzene difluorobiphenyl 2.330 20 chlorobenzene dichlorobiphenyl 420 2 l (trifluorobis( trifluoromethyl 660 methyl)benzene biphenyl 22 nitrobenzene dinitrobiphenyl 2.470 23 phenylacetate diacetoxybiphenyl 5,720

EXAMPLES 24-31 300ml of o-xylene and organic palladium compounds shown in Table 3. together with an additive were introduced into a stainless steel autoclave of 1,000ml capac ity. gaseous mixture of nitrogen and oxygen (1 l mol ratio) was introduced into it till the pressure reached 50 kg/cm and an oxydative coupling reaction was carried out at 150C for 7 hours.

After the reaction, the solution was treated in a similar way to Example 1 and was analyzed by means of gas-chromatography, thus tetramethylbiphenyl was obtained as shown in Table 3.

Table 4 yield of tetramethylbiphenyl palladium based on Control compound (m additive organic palladium mol) (rn mol) compounds (mol 7t 7 palladium dimethyl- 0 acetate (2) formamide lo 100) 8 palladium cyclo- 0 acetate (2) octadiene What is claimed is:

1. A catalytic coupling process which comprises dehydrogenatively coupling a reactive aromatic compound having at least two hydrogen atoms in the aromatic nucleus and represented by the following general formula:

wherein R is selected from the group consisting of a hydrogen atom, alkyls having 1 to 5 carbon atoms, alkanoyloxy having I to 5 carbon atoms, alkoxys having 1 to 5 carbon atoms, acetyl or halogen substituted al- 300ml of o-xylene. 2m mols of palladium acetate and 2m mols of sulfuric acid were introduced into the autoclave in a similar way to Example 24 and a reaction was carried out, but no coupled compound was obtained. Controls 7, 8

Dimethylformamide or cyclooctadiene was used in stead of sulfuric acid in the Example 24 and the res of the reaction are shown in Table 4,

kyl. nitro and halogen, and n is 0 to 4, under the pressure of a gas selected from the group consisting of oxygen and oxygen-containing gas in the presence of an organic palladium compound and a member selected from the group consisting of B-diketone and ethylenediamine-tetraacetic acid in the amount of 0.5

1 mols based on the organic palladium compound,

1 in the absence of a compound selected from the gnuconsisting of sodium acetate, potassium acetate,

lithium chloride, potassium nitrate, lithium nitrate, potassium sulfate, acetic acid, sulfuric acid, a polar solvent and water, the partial pressure of the oxygen being at least about kg/cm 2. A process of claim 1, wherein the oxygencontaining gas is selected from the group consisting of mixtures of elemental oxygen and nitrogen gas, carbon dioxide and rare element gases.

3. A process of claim 1, wherein the partial pressure of oxygen is within the range of 5 to 300 kg/cm 4. A process of claim 1, wherein the organic palladium compound is selected from the group consisting of an organic palladium salt of aliphatic monocarboxylic acid having I 5 carbon atoms, palladium range from room temperature to 300C. 

1. A CATALYTIC COUPLING PROCESS WHICH COMPRISES DEHYDROGENATIVELY COUPLING A REACTIVE AROMATIC COMPOUND HAVING AT LEAST TWO HYDROGEN ATOMS IN THE AROMATIC NUCLEUS AND REPRESENTED BY THE FOLLOWING GENERAL FORMULA:
 2. A process of claim 1, wherein the oxygen-containing gas is selected from the group consistIng of mixtures of elemental oxygen and nitrogen gas, carbon dioxide and rare element gases.
 3. A process of claim 1, wherein the partial pressure of oxygen is within the range of 5 to 300 kg/cm2.
 4. A process of claim 1, wherein the organic palladium compound is selected from the group consisting of an organic palladium salt of aliphatic mono-carboxylic acid having 1 - 5 carbon atoms, palladium benzoate, palladium acetylacetonate and bisdibenzylideneacetone palladium.
 5. A process of claim 4, wherein the concentration of the organic palladium compound is 1/10 to 1/10.000 mol based on the aromatic compounds.
 6. A process of claim 1, wherein the aromatic compound is selected from the group consisting of toluene, o-xylene, nitrobenzene, phenyl acetate, and fluorobenzene.
 7. A process of claim 1, wherein the aromatic compound is coupled at a reaction temperature within the range from room temperature to 300*C. 